Coreless Banking: When Your Core Stops Being a Single Platform

WAU Marketing
Jul 30
4 min read

Here's an idea that makes half the industry uncomfortable: the best core for your bank might be not having a single core. Not "no" core—that's a misunderstanding—but to stop betting everything on one monolithic platform and instead orchestrate specialized capabilities you can swap without tearing down the rest.

We've already written about composable banking on this blog: assembling your platform from modular blocks connected by API. Coreless banking is the next rung of that same idea, pushed to the extreme. It isn't buying one giant core that does everything "pretty well"; it's choosing, for each function—ledger, pricing, origination, payments, fraud prevention—the best available component, and making them all talk to each other. The core stops being a building and becomes a network.

What "coreless" means (and what it doesn't)

The term wasn't coined by a vendor; it was formalized by the Banking Industry Architecture Network (BIAN), a nonprofit banking-architecture standards body. In its definition, "coreless" doesn't mean running without a core, but that core functions are accessed through an independent banking domain layer, via well-defined APIs and a standard message model, per BIAN itself. Translated: each piece exposes what it does through standard contracts, so the bank can "select the software vendors needed to obtain the best-of-breed for each application area without worrying about interoperability," BIAN explains.

Consultancy Thoughtworks frames it with a useful distinction: separate commodity functions—the ones that don't differentiate you, like running the ledger—from the differentiating capabilities that actually compete for the customer. The former live in a headless ledger; the latter, in that domain layer where you build your offering from the best components, Thoughtworks argues. Coreless, then, isn't a marketing fad: it's an architectural decision about where to put each thing.

How we got here: from proof of concept to a living standard

This isn't whiteboard theory. BIAN has iterated the concept across successive versions with real banks and vendors. Its 2.0 version (2021) focused on interoperability, translating proprietary message models into BIAN's standard model; 3.0 added customer consent for a full view of their financial position, BIAN documents. And in October 2024 it unveiled Coreless Banking 4.0, which uses AI and machine learning to spot at-risk customers and personalize retention offers, in work with Wells Fargo, Bangkok Bank, Bantrab, IBM, Salesforce, Zafin, TCS and Temenos, among others, according to BIAN's announcement. That banks of that size sit down to test the model says something: the question is no longer "if," but "how."

Why it matters now: composability is no longer optional

The context pushes the same way. Gartner anticipated that by 2024, 60% of finance organizations would seek composable finance applications in their new technology investments, per a Gartner press release. Composability—modular blocks and packaged business capabilities connected by API—went from differentiator to the baseline buyers expect.

And the pressure is especially real in our region. Up to 60% of core banking systems in Latin America still run on legacy technology that is costly and vulnerable, Galileo Financial Technologies estimates. The cost shows up as speed: a traditional bank can take up to 12 months to launch a new product, versus 3 to 6 months for a fintech, per the same firm. When your competition ships twice as fast, architecture stops being an IT topic and becomes a commercial-survival one.

That's why a prudent middle pattern is gaining ground: the sidecar core, a modern cloud-native core that runs alongside the legacy one and gradually takes over services. IDC projects that 40% of the world's banks will adopt sidecar core strategies by 2026, Galileo reports. It is, in practice, an on-ramp to coreless without a big bang.

The uncomfortable side: orchestration and governance

We'd be dishonest if we sold coreless as magic. Decoupling has a price, and you pay it in complexity. When your bank is a composition of modules from different providers, the orchestration between them—getting them to talk, keeping data consistent, avoiding silos—becomes the new hard work, services firm NTConsult warns. Without a governance framework, concrete risks appear: version drift across services, uncoordinated dependencies, and fragmented observability, per NTConsult.

And every component you add widens the attack surface, demanding security discipline across all modules, plus active management of each vendor relationship to avoid a new kind of lock-in, notes vendor i-exceed. The lesson is clear: coreless doesn't eliminate complexity, it relocates it. You move from "one monolith that's hard to change" to "many pieces that are easy to change but hard to govern." Without the orchestration layer, standardized API contracts, and data governance, what you gain in flexibility you lose in chaos.

When it fits (and when it doesn't)

Coreless isn't for everyone, nor for everything, at once. It fits when a capability genuinely differentiates you and you want the market's best component without tying yourself down; when you need to launch and experiment fast; when legacy is slowing you product by product. Don't force it onto commodity functions a solid ledger already handles well, and don't do it without the operational maturity to orchestrate and govern. The good news: it isn't all-or-nothing—starting with a thin slice, a single use case end-to-end, is exactly what serious architects recommend, as Thoughtworks proposes.

How we see it at WAU

At WAU we don't believe in the eternal monolith or in "buy everything from one vendor." We believe in a modern core that's coreless-ready: a reliable headless ledger for the commodity, and a domain layer with standardized APIs, events, and governance so you can plug in best-of-breed where you actually compete. That's what makes the rest possible: swapping a component without rewriting the bank, launching in weeks instead of quarters, and growing without chaining yourself to a single platform.

Coreless isn't having no core. It's no longer depending on just one. If you want to see what in your architecture is already ready to be composed and what's holding you back, let's talk. 👉 Book a conversation with our team.